In 2009, the Pentagon introduced what's known as the Golden Hour Policy, directing that soldiers with critical injuries be transported by helicopter from the battlefield to a treatment center within an hour. The previous standard was two hours.

Researchers analyzed data from more than 21,000 U.S. military casualties that occurred in Afghanistan between September 2001 and March 2014.

Over that time, the killed-in-action rate fell from 16 percent to about 10 percent; the case fatality rate dropped from 13.7 percent to 7.6 percent; and the rate of death from wounds remained unchanged at just over 4 percent.

The reduction in case fatalities was associated with an increase in the number of wounded soldiers being transported to a treatment center within an hour, saving nearly 360 lives, according to the study published online Sept. 30 in the journal JAMA Surgery.

Data from more than 4,500 wounded soldiers showed that median helicopter transport time fell from 90 minutes to 43 minutes over the period. The number of casualties who arrived at a treatment facility within an hour rose from about 25 percent to 75 percent.

The researchers also found that the percentage of critically injured troops killed in action was lower among those who received a blood transfusion and were transported in an hour or less, and the percentage who died of wounds was lower among those initially treated by combat support hospitals.

"Decreasing the time from injury to arrival at the treatment facility challenged the full measure of the trauma system with more critically injured casualties who then benefited from the care they received," wrote study author Dr. Russ Kotwal and colleagues at the U.S. Army Institute of Surgical Research at Joint Base San Antonio-Fort Sam Houston in San Antonio, Texas.

In an accompanying editorial, Dr. Todd Rasmussen of the U.S. Combat Casualty Care Research Program at Fort Detrick, Md., wrote: "Reduction in the percentage killed in action following the 2009 policy change provides evidence of the effect of an enhanced capability during the 'golden hour' after injury."